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Abstract:

A sheet conveyance device includes a support unit that supports a sheet;
plural suction ports placed on the support unit; a suction unit that
suctions the sheet toward the support unit, the suction unit being
connected to the plural suction ports; plural valve systems, each valve
system being placed between the corresponding suction port and the
suction unit, each valve system being openable and closeable; plural
valve interlocked suction ports that are to be covered by the sheet when
the sheet is conveyed, the plural valve interlocked suction ports being
arranged separately from the plural suction ports; and plural opening and
closing units that open and close the plural valve systems, each opening
and closing unit being placed between one of the valve interlocked
suction ports and one of the valve systems.

Claims:

1. A sheet conveyance device comprising: a support unit that supports a
sheet; plural suction ports placed on the support unit; a suction unit
configured to suction the sheet toward the support unit, the suction unit
being connected to the plural suction ports; plural valve systems, each
of the valve systems being placed between the corresponding suction port
and the suction unit, each of the valve systems being openable and
closeable; plural valve interlocked suction ports that are to be covered
by the sheet when the sheet is conveyed, the plural valve interlocked
suction ports being arranged separately from the corresponding suction
ports; and plural opening and closing units configured to open and close
the corresponding valve systems, each of the opening and closing units
being placed between one of the valve interlocked suction ports and one
of the corresponding valve systems.

2. The sheet conveyance device according to claim 1, wherein the plural
suction ports and the plural valve interlocked suction ports are arranged
in a width direction of the sheet.

3. The sheet conveyance device according to claim 1, wherein the plural
valve interlocked suction ports are arranged at an upstream side of the
corresponding suction ports in a sheet conveyance direction.

4. The sheet conveyance device according to claim 1, wherein the plural
suction ports are connected to the suction unit through corresponding
fluid channels, and each of the valve systems is placed on the
corresponding fluid channel, and wherein the plural valve interlocked
suction ports are arranged at an upstream side and a downstream side of
the plural suction ports in a sheet conveyance direction.

5. The sheet conveyance device according to claim 1, wherein the plural
suction ports are arranged in a sheet conveyance direction.

6. The sheet conveyance device according to claim 1, wherein each of the
valve interlocked suction ports is associated with a corresponding
portion of the plural suction ports.

7. The sheet conveyance device according to claim 1, wherein each of the
opening and closing units is configured to open the corresponding valve
system, when a pressure difference between an atmospheric pressure and a
pressure inside the corresponding valve interlocked suction port is
greater than or equal to a constant value.

8. The sheet conveyance device according to claim 1, wherein a check
valve is arranged between each of the opening and closing units and the
suction unit.

9. The sheet conveyance device according to claim 1, wherein each of the
opening and closing units includes a flexible member, and wherein each of
the valve systems is opened when the sheet covers the corresponding
suction port and the corresponding flexible member is deformed.

10. The sheet conveyance device according to claim 1, wherein the sheet
conveyance device conveys plural of the sheets while the plural sheets
are evenly spaced apart in a conveyance direction in which the plural
sheets are conveyed or a width direction perpendicular to the conveyance
direction.

11. An image forming device comprising: a sheet conveyance device,
wherein the sheet conveyance device includes a support unit that supports
a sheet; plural suction ports placed on the support unit; a suction unit
configured to suction the sheet toward the support unit, the suction unit
being connected to the plural suction ports; plural valve systems, each
of the valve systems being placed between the corresponding suction port
and the suction unit, each of the valve systems being openable and
closeable; plural valve interlocked suction ports that are to be covered
by the sheet when the sheet is conveyed, the plural valve interlocked
suction ports being arranged separately from the corresponding suction
ports; and plural opening and closing units configured to open and close
the corresponding valve systems, each of the opening and closing units
being placed between one of the valve interlocked suction ports and one
of the corresponding valve systems.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] Embodiments of the present invention relate to a recording device
which forms an image on a sheet. Specifically, the embodiments of the
present invention relate to a conveyance device having a suction
conveyance unit that suctions and conveys various sizes of sheets of
materials, which are recording media, using airflows.

[0003] 2. Description of the Related Art

[0004] In a conveyance device used for an image forming device, such as a
conventional inkjet printer, when an image is formed, it may be necessary
to maintain a constant spacing between a recording unit and a recording
medium. Thus, it is not possible to convey the recording medium while
holding the recording medium. Therefore, when the recording medium is
conveyed, it may be necessary that a deformation or a lifting of the
recording medium is regulated. Further, during an image forming process,
when a deformation of the recording medium itself occurs, for example,
when stretching of the recording medium associated with adhesion of ink
(hereinafter, referred to as stretching) or deformation of the recording
medium associated with application of heat occurs, it may be necessary to
provide a groove portion so that the deformation of the recording medium
is released to the opposite side of the recording unit. As described
above, the following conveyance device is known. Namely, as shown in FIG.
8, the conveyance device supports the reverse side of the recording
medium on a conveyance surface in an image forming area. Further, the
conveyance device includes plural suction ports for suctioning the
recording medium from the reverse side, so as to prevent the recording
medium from being lifted. The conveyance device conveys the recording
medium while suctioning the recording medium in the image forming area.

[0005] In the above described conveyance device, when the recording medium
is conveyed to a position where the recording medium covers all the
suction ports 22 of orifices 14, which are arranged on the conveyance
surface, since inside of each orifice 14 is sealed, a negative pressure
increases and the suction force increases. In this manner, a deformation
of the recording medium which exists prior to forming an image or a
deformation of a recording medium caused by adhered ink when forming the
image is suppressed, and the recording medium can be stably conveyed.
Further, since the orifice 14 has a constant length, when a deformation,
such as the stretching, occurs on the recording medium, an amount of the
deformation can be released to the reverse side of the recording unit by
the suction force.

[0006] However, at a position shown in FIG. 9, where the recording medium
only covers suction ports 22 placed at a front tip or a rear tip of the
orifice 14, the air is suctioned through suction ports 22 which are
released. Thus, there is a problem that a lifting or a deformation of the
recording medium is not sufficiently regulated, since the negative
pressure inside the orifice 14 does not increase and the suction force
does not increase. Therefore, techniques for controlling a suction force
acting onto the recording medium or a suction timing to suction the
recording medium in the above described conveyance device are disclosed,
for example, in Patent Document 1 (Japanese Published Unexamined
Publication No. S64-43430), Patent Document 2 (Japanese Published
Unexamined Publication No. H09-058897), and Patent Document 3 (Japanese
Registered Patent No. 3690182).

[0007] Patent Document 1 discloses a technique such that, when a sheet
covers suction ports, an output of a pump is reduced so as to prevent a
suction force from becoming rapidly large. However, in this
configuration, the air is always suctioned through suction ports other
than the suction ports conveying the sheet. In such a case, it may be
necessary to adjust the suction force of the pump, so that the sheet is
surely conveyed, even if the sheet does not cover all the suction ports.
Thus a large pump tends to be used. Therefore, the configuration
disclosed in Patent Document 1 has problems that the device becomes
large, and noise and cost increase.

[0008] Patent Document 2 discloses a technique for avoiding unnecessary
suctioning. In the technique, for the suction ports other than the
suction ports conveying the sheet, a driving means for opening and
closing a valve system and a sensor are used, so as to selectively avoid
unnecessary suctioning. With this configuration, the size of the pump can
be reduced. However, for example, when a surface for suctioning the sheet
is large, in order to selectively avoid unnecessary suctioning at finer
areas so as to prevent tips of the sheet from lifting, it may be
necessary to place plural driving units for opening and closing the valve
system. This leads to complication of the device and growth in size of
the device. Further it can be a cause of a cost increase.

[0009] Patent Document 3 discloses a technique using a pressure adjustment
valve. Namely, when a sheet covers a suction port, the pressure
adjustment valve causes a suction force to be generated, and when the
sheet does not cover the suction port, the pressure adjustment valve does
not allow unnecessary suctioning to be performed. However, in this
technique, a suction force is not obtained until the sheet completely
covers an orifice (a suction port). Thus, the suction force at the tip of
the sheet is always weaker than the suction force at the center of the
sheet. Therefore, there is a problem that the technique does not handle
the lifting of the tips of the sheet. Further, in this technique, the
pressure adjustment valve is closed by fluid flow (wind). However, when
the pressure adjustment valve is closed, the fluid does not flow, and the
pressure adjustment valve is opened. Patent Document 3 does not disclose
a technique to overcome this problem. However, as a technique to overcome
this problem, a method in which the valve unit is not completely closed
and the valve unit partially leaks the fluid, or a method of completely
closing the pressure adjustment valve by a pressure difference between a
suction side and an orifice side, the pressure adjustment valve being
pinched between the suction side and the orifice side, can be considered.
However, when the pressure adjustment valve is not completely closed,
since not all the unnecessary suctioning is stopped, inefficiency of the
suctioning remains. Further, in the method of completely closing the
pressure adjustment valve by the pressure difference between the suction
side and the orifice side, at an instant when the recording medium covers
the orifice, the pressure difference for closing the pressure adjustment
valve is not released, and the pressure adjustment valve is not opened.
When the pressure inside the orifice is increased by leakage through a
gap between the orifice and the recording medium, the pressure adjustment
valve is opened. Therefore, the problem that the technique does not
handle the lifting of the tips of the sheet remains. Further, in order to
cause the pressure adjustment valve to be opened when a sheet covers a
portion of an orifice, a valve may be opened and closed in response to a
very small pressure difference or a very small flow difference of a
fluid. Therefore, a highly precise valve system may be required, and a
suction force from a suction mechanism may be very precise. Such a
technique is not realistic, and it leads to problems, such as a cost
increase, degradation of proccessability, and growth in size of the
device.

SUMMARY OF THE INVENTION

[0010] In one aspect, there is provided a sheet conveyance device
including a support unit that supports a sheet; plural suction ports
placed on the support unit; a suction unit that suctions the sheet toward
the support unit, the suction unit being connected to the plural suction
ports; plural valve systems, each valve system being placed between the
corresponding suction port and the suction unit, each valve system being
openable and closeable; plural valve interlocked suction ports that are
to be covered by the sheet when the sheet is conveyed, the plural valve
interlocked suction ports being arranged separately from the plural
suction ports; and plural opening and closing units that open and close
the plural valve systems, each opening and closing unit being placed
between one of the valve interlocked suction ports and one of the valve
systems.

[0011] In another aspect, there is provided an image forming device
including a sheet conveyance device. The sheet conveyance device includes
a support unit that supports a sheet; plural suction ports placed on the
support unit; a suction unit that suctions the sheet toward the support
unit, the suction unit being connected to the plural suction ports;
plural valve systems, each valve system being placed between the
corresponding suction port and the suction unit, each valve system being
openable and closeable; plural valve interlocked suction ports that are
to be covered by the sheet when the sheet is conveyed, the plural valve
interlocked suction ports being arranged separately from the plural
suction ports; and plural opening and closing units that open and close
the plural valve systems, each opening and closing unit being placed
between one of the valve interlocked suction ports and one of the valve
systems.

[0012] Other objects, features and advantages of the present invention
will become more apparent from the following detailed description when
read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a schematic diagram of a major portion of an inkjet
recording device, to which an embodiment of the present invention can be
applied;

[0014]FIG. 2 is a schematic diagram of a conveyance device used in a
first embodiment of the present invention;

[0015]FIG. 3 is a schematic diagram illustrating an opening and closing
unit used in the first embodiment of the present invention;

[0016]FIG. 4 is a schematic diagram illustrating the opening and closing
unit used in the first embodiment of the present invention;

[0017]FIG. 5 is a schematic diagram of a conveyance device used in a
second embodiment of the present invention;

[0018]FIG. 6 is a schematic diagram of a conveyance device used in a
third embodiment of the present invention;

[0019] FIG. 7 is a schematic diagram of a conveyance device used in a
fourth embodiment of the present invention;

[0022] It is an objective of embodiments of the present invention to solve
the above described problems. Further, it is an objective of the
embodiments of the present invention to provide a conveyance device that
can suction a sheet immediately before the sheet covers a suction port,
that can keep suctioning the sheet until the sheet is completely
separated from the suction port, that can surely prevent the sheet from
lifting, and that can perform efficient and stable sheet conveyance,
without additionally arranging a sensor or an actuator.

[0023]FIG. 1 is a schematic diagram of an inkjet recording device 10,
which is an image forming device to which an embodiment of the present
invention can be applied. The inkjet recording device 10 includes a
carriage 21 which can reciprocate in a main scanning direction. Here, the
main scanning direction is a width direction of a recording paper, and
the main scanning direction is perpendicular to a conveyance direction of
the recording paper. The carriage 21 includes a recording head (not shown
in the figure) which discharges black ink, magenta ink, cyan ink, and
yellow ink. A guide plate 23 is placed at upstream side of the carriage
21 in the conveyance direction of the recording paper. The guide plate 23
serves as a supporting unit. On an upper surface of the guide plate 23, a
recording paper is conveyed. As shown in FIG. 2, plural orifices 24 are
formed on the guide plate 23. The plural orifices 24 are formed in a
conveyance direction of a sheet 1 and in a width direction of the sheet
1. Here, the sheet 1 is conveyed on the guide plate 23. A suction port 25
is formed inside each orifice 24. The suction port 25 is connected to a
suction unit 20 which incorporates a pump. Further, an openable and
closeable valve system 26 is placed between the suction port 25 and the
suction unit 20.

[0024] A valve interlocked suction port 27 is placed at upstream side of
the corresponding suction port 25 on the guide plate 23 in the conveyance
direction of the sheet 1. The valve interlocked suction port 27 is
connected to the suction unit 20. In the channel connecting the valve
interlocked suction port 27 and the suction unit 20, an opening and
closing unit 28 for opening and closing the valve system 26 is placed. As
shown in FIG. 3, the opening and closing unit 28 includes a flexible
member 30 which is arranged in an air chamber 29. The flexible member 30
is placed at one side of the air chamber 29. The flexible member 30 is
connected to one end of an on-off valve 31, which is included in the
valve system 26. The valve system 26 includes the L shaped on-off valve
31. A bent portion of the on-off valve 31 is rotatably attached to a wall
portion of a flow channel connected to the suction unit 20. Further, a
pair of conveyance rollers 32 for conveying the sheet 1 is placed at
upstream side of the valve interlocked suction port 27 in the conveyance
direction of the sheet 1. Additionally, a pair of conveyance rollers 33
for conveying the sheet 1 is placed at downstream side of the orifice 24
in the conveyance direction of the sheet 1.

[0025] With the above described configuration, in a state shown in FIG. 3
in which the sheet 1 has not reached the valve interlocked suction port
27, since the on-off valve 31 blocks the flow channel, a suction force
does not act at the suction port 25, even if the suction unit 20 is
working. In this case, the suction force only acts at the valve
interlocked suction port 27. When the valve interlocked suction port 27
is blocked by the conveyed sheet 1 as shown in FIG. 4, the pressure
inside the air chamber 29 becomes a negative pressure by the operation of
the suction unit 20. Thus the flexible member 30 is deformed. With the
deformation of the flexible member 30, the on-off valve 31 connected to
the flexible member 30 rotates and the flow channel is released. Then the
suction force from the suction unit 20 also acts at the suction port 25.

[0026] In the above described embodiment 1, the air is suctioned prior to
the front tip of the sheet 1 reaching the orifice 24. When the front tip
of the sheet 1 reaches the orifice 24, a sufficient suction force from
the suction unit 20 is acting. Therefore, by using a lower cost
configuration in which sensors or electrical driving mechanisms are not
used, the sheet 1 can be stably conveyed while the lifting of the front
tip of the sheet 1 is prevented. Further, plural of the suction ports 25
and plural of the valve interlocked suction ports 27 are arranged in the
width direction of the sheet 1. Therefore, when a sheet having a
different width is conveyed, an unnecessary suction is not performed, and
the sheet can be stably conveyed while the lifting of the sheet is
prevented. Further, since the valve interlocked suction port 27 is placed
at upstream side of the suction port 25 in the sheet conveyance
direction, it is ensured that the front tip of the sheet 1 is suctioned
first. Therefore, the sheet 1 can be stably conveyed while the lifting of
the tip of the sheet 1 is surely prevented. Further, since the plural
suction ports 25 are also arranged in the sheet conveyance direction, an
unnecessary suction is not performed when an image is formed over a long
distance in the sheet conveyance direction. Therefore, the sheet 1 can be
stably conveyed while the lifting of the tip of the sheet 1 is prevented.
Further, when a pressure difference between the atmospheric pressure and
the pressure inside the valve interlocked suction port 27 is greater than
a predetermined value, the opening and closing unit 28 opens the on-off
valve 31. Therefore, the valve system 26 can be opened and closed more
reliably.

[0027] In the embodiment, the valve interlocked suction port 27 is
arranged at downstream side of the pair of conveyance rollers 32 in the
sheet conveyance direction. However, the position of the valve
interlocked suction port 27 is not limited to this. It is preferable that
the valve interlocked suction port 27 be arranged at a suitable position
depending on a conveyance speed of the sheet 1, or a layout of the inkjet
recording device 10. Further, in the configuration of the embodiment, the
flexible member 30 is used in the opening and closing unit 28. However, a
piston mechanism can be used instead of the flexible member 30.

[0028]FIG. 5 shows a second embodiment of the present invention. Compared
to the first embodiment, the second embodiment is different from the
first embodiment in the following points. A valve interlocked suction
port 34 is arranged at downstream side of the orifice 24 in the sheet
conveyance direction. At the same time, in a flow channel connecting the
valve interlocked suction port 34 and the suction unit 20, an opening and
closing unit 35 similar to the opening and closing unit 28 is arranged.
The flow channel connecting the suction port 25 and the suction unit 20
is divided into two flow channels. The valve system 26 is arranged in the
first flow channel, and the valve system 36 similar to the valve system
26 is arranged in the second flow channel. The valve system 26 is opened
and closed by the opening and closing unit 28, and the valve system 36 is
opened and closed by the opening and closing unit 35.

[0029] With the above described configuration, in addition to the effect
of the first embodiment, the following effects can be obtained. Namely,
in the state shown in FIG. 5 in which the end tip of the sheet 1 is not
completely covering the orifice 24, since the sheet 1 is covering the
valve interlocked suction port 34, the suction force from the suction
unit is acting at the suction port 25. Therefore, the air is suctioned
from the suction port 25 after the end tip of the sheet 1 has passed
through the upstream end portion of the orifice 24. Therefore, by using a
low cost configuration in which sensors or electrical driving mechanisms
are not used, the sheet 1 can be stably conveyed while the lifting of the
end tip of the sheet 1 is prevented. Further, with such a configuration,
an unnecessary suction that might be performed after the end tip of the
sheet 1 is completely separated from the orifice 24 can be avoided.

[0030]FIG. 6 shows a third embodiment of the present invention. In the
third embodiment, plural orifices 24 are arranged in the sheet conveyance
direction. The valve interlocked suction port 27 is arranged at upstream
side of an orifice 24-1 in the sheet conveyance direction. Here, the
orifice 24-1 is arranged at the upstream most position among the plural
orifices. A valve mechanism 26-1 arranged in a first flow channel of
first divided flow channels is opened and closed by an opening and
closing unit 28-1 which is arranged between the valve interlocked suction
port 27 and the suction unit 20. The valve interlocked suction port 34 is
arranged at downstream side of an orifice 24-2 in the sheet conveyance
direction. Here, the orifice 24-2 is arranged at the downstream most
position among the plural orifices. A valve mechanism 36-2 arranged in a
second flow channel of second divided flow channels is opened and closed
by an opening and closing unit 35-2 which is arranged between the valve
interlocked suction port 34 and the suction unit 20. At a position where
the orifices 24-1 and 24-2 are neighboring each other, an opening and
closing unit 35-1 arranged in the second flow channel of the first
divided flow channels of the upstream side orifice 24-1 opens and closes
a valve mechanism 26-2 arranged in the first flow channel of the second
divided flow channels of the downstream side orifice 24-2. Further, an
opening and closing unit 28-2 arranged in the first flow channel of the
second divided flow channels of the downstream side orifice 24-2 opens
and closes a valve mechanism 36-1 arranged in the second flow channel of
the first divided flow channels of the upstream side orifice 24-1.
Further, check valves 37 are arranged at a downstream position of the
opening and closing unit 28-1, a downstream position of a position at
which the first divided flow channels of the upstream side orifice 24-1
meet, a downstream position of a position at which the second divided
flow channels of the downstream side orifice 24-2 meet, and a downstream
position of the opening and closing unit 35-2, respectively.

[0031] With the above described configuration, when plural orifices are
densely arranged, a valve system arranged in a first orifice can be
opened and closed by a pressure difference between the atmospheric
pressure and the pressure in a second orifice, which is neighboring to
the first orifice, without introducing a new valve interlocked suction
port. Therefore, a stable conveyance can be realized without cost
increase. Further, since check valves are provided, even if the suction
ports 25 neighboring to each other are opened, the valve mechanisms 26,
35 can be surely operated.

[0032] FIG. 7 shows a fourth embodiment of the present invention. In this
embodiment, one valve interlocked suction port 27 is placed for plural
suction ports 25. Specifically, for the plural suction ports 25 included
in an area A of central six rows, a valve interlocked suction port 27-1
is arranged. For the plural suction ports 25 included in an area B of
upper two rows, a valve interlocked suction port 27-2 is arranged.
Further, for the plural suction ports 25 included in an area C of lower
two rows, a valve interlocked suction port 27 is arranged. When the valve
interlocked suction port 27-1 is covered with the sheet 1, the suction
ports 25 included in the area A start suctioning. When the valve
interlocked suction port 27-2 is covered with the sheet 1, the suction
ports 25 included in the area B start suctioning. Further, when the valve
interlocked suction port 27 is covered with the sheet 1, the suction
ports 25 included in the area C start suctioning.

[0033] In the above configuration, when types of the sheet 1 are limited
to several types, and, for example, when the sheet 1 is conveyed while
the sheet 1 is aligned to the central portion, the width of the area A
may be adjusted to be a width of the smallest type of the sheet 1 to be
conveyed. Further, it is not necessary that a valve interlocked suction
port 27 be placed for each suction port 25. With the above configuration,
cost reduction may be achieved. Additionally, the above configuration is
advantageous as a layout of the inkjet recording device 10.

[0034] With the configurations shown in the embodiments, when plural
sheets 1 are conveyed while the sheets 1 are evenly spaced apart in the
conveyance direction or in the width direction, it is possible to cause
the suction ports 25, above which the sheets 1 do not exist, not to
suction, and cause the only suction ports 25, to which the sheets 1 are
to be conveyed immediately after, to suction. Therefore, recording papers
are efficiently suctioned, and the recording papers can be stably
conveyed. Further, when an image is formed by a single scanning across
the spacing of the sheets (for example, when the sheets are conveyed
while the sheets are evenly spaced apart in the conveyance direction, a
case in which an image is formed by a single scanning of a rear end
portion of the front sheet and a front end portion of the successive
sheet), an occurrence of an air current caused by the suction can be
minimized by eliminating redundant suction operations, which are the
suction operations between the sheets. In this case, adverse effects on
ink discharge caused by the occurrence of the air current can be reduced.

[0035] The present invention is not limited to the specifically disclosed
embodiments, and variations and modifications may be made without
departing from the scope of the present invention.

[0036] The present application is based on Japanese Priority Application
No. 2011-011092, filed on Jan. 21, 2011, the entire contents of which are
hereby incorporated herein by reference.

Patent applications by Yoichi Ito, Tokyo JP

Patent applications by Yuji Tanaka, Kanagawa JP

Patent applications in class By means to convey sheet (e.g., from pack to operation)

Patent applications in all subclasses By means to convey sheet (e.g., from pack to operation)